Understanding Solder Ratios

The ratio of soldering typically refers to the composition of the solder alloy, specifically the percentage of the metals it contains. Common ratios used in electronics soldering are 63/37 and 60/40, representing the proportion of tin to lead.

When discussing the ratio of soldering, it primarily relates to the mix of metals that make up the solder wire or paste. Historically, and still commonly in some applications, solder is an alloy of tin (Sn) and lead (Pb). The ratio indicates the percentage of each metal by weight.

Common Solder Ratios

Based on common usage and the provided reference, two ratios are particularly prevalent for hand soldering in electronics:

• 63/37 Tin/Lead: This is a very popular ratio, known as eutectic solder.
• 60/40 Tin/Lead: Another widely used ratio.

These ratios offer different melting characteristics crucial for effective soldering.

The 63/37 Eutectic Ratio

The 63/37 ratio is particularly notable. As mentioned in the reference:

The 63/37 ratio, known as eutectic solder, has practically no plastic range and melts almost instantly at 183 C -361 F.

This means that 63/37 solder transitions directly from solid to liquid at a single temperature (183°C or 361°F) without going through a semi-solid (plastic) phase. This characteristic is highly desirable in soldering as it helps create strong, shiny solder joints and minimizes the risk of "cold" joints caused by movement while the solder is solidifying in a plastic state.

The 60/40 Ratio

The 60/40 tin/lead solder is also widely used. Unlike the 63/37 eutectic solder, 60/40 solder has a small plastic range where it is semi-solid before fully solidifying. This can sometimes be advantageous in specific applications but requires careful handling during the cooling process.

Here's a quick look at the common ratios:

In summary, the "ratio of soldering" refers to the specific composition of the solder alloy, with 63/37 and 60/40 being two of the most common examples, each with distinct properties.